Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$195.93	13.856%	$223.0781	$223.08	$223.10	$223.10
Purchase #2	$10.41	3.822%	$10.8079	$10.81	$10.80	$10.80
Purchase #3	$17.37	8.789%	$18.8966	$18.90	$18.90	$18.90
Purchase #4	$89.59	10.250%	$98.773	$98.77	$98.75	$98.80
Purchase #5	$200.35	3.527%	$207.4163	$207.42	$207.40	$207.40
Purchase #6	$40.77	5.133%	$42.8627	$42.86	$42.85	$42.90
Purchase #7	$235.57	8.591%	$255.8078	$255.81	$255.80	$255.80
7 purchase totals =	$789.99		$857.6424	$857.65	$857.60	$857.70